This trophy is earned between the levels 'Magic is Might' and 'In Grave Danger'. Use the map in the tent to travel to Hogwarts. The tent also appears between 'In Grave Danger' and 'Sword and Locket'. After you complete year 7, Hogwars reverts back to normal.

This is my first post ever on any game. It was my last trophy so i replayed the story only to find the Hogwarts train was missing. The Vanishing Cabinet at B+Bs in Knockturn Alley wouldnt open? Then I accidently found the answer. Inside your tent in the campsite hub (the big tent with the apparition point back to London. The tent that Harry and Hermione dance together in.)is a map all folded up. It has a lit circle on the floor next to it. THIS takes you back to Hogwarts and the trophy is instant. That was my 99nth completed ps3 game.

listen lol , the very first time you see the tent (deathly hallows part1) go inside that tent, then simply use the left side orange circle ( book ) youlbe teleported to the past and trophy will pop, very easy lol

btw lol, i dont see where you see that "magic is might" or "grave danger" when you press start you will see at bottom of the screen "deathly hallows part1" so like i said, the very first time you see the tent go inside and select left side book